import java.util.Scanner;

/**
 * @author gao
 * @date 2025/11/18 10:37
 */

public class Solution {
    public int sumOfUnique(int[] nums) {
        int[] hashset = new int[101];
        int sum = 0;

        for (int i : nums) {
            hashset[i]++;
        }

        for (int i = 0; i < hashset.length; i++) {
            if (hashset[i] == 1) {
                sum += i;
            }
        }
        return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int n = in.nextInt();
            int[] nums = new int[n];
            for (int i = 0; i < n; i++) {
                nums[i] = in.nextInt();
            }
            Solution solution = new Solution();
            System.out.println(solution.sumOfUnique(nums));
        }
    }
}